The present invention relates to a battery comprising a device for the digital transmission of current measurement values and to a battery controller comprising a device for receiving a digital transmission of current measurement values.
In battery systems, great importance is being placed on the measurement of battery current in determining the charging state as well as in ensuring a reliable operation, in order to prevent a potentially dangerous condition. There is a plurality of dangers which can be attributed to an inadmissible current. Such dangers include inter alia an overload of the battery, an excess current or a lithium plating.
In the event of overloading the battery, more current is provided to the battery than the current state of the battery allows (e.g. due to the current temperature or the state of ageing of the battery). This can possibly lead to the battery overheating and can end in a dangerous situation.
In the event of excess current, more current is provided by the battery than the individual cells can deliver (above the specification). This can also result in the battery overheating.
Charging the battery at very low temperatures with high currents causes metallic lithium to deposit. This is referred to as lithium plating. Lithium plating can also be dangerous because this effect can lead to a short circuit in the battery. A monitoring of the lithium plating is particularly critical because just a few amperes too much can lead to an undetected fault in the battery.
Due to the dangers described and others, it is necessary to reliably measure a current. A safety rating of the current measurement according to ASIL C (IS026262) ensues from a danger and risk analysis. A single channel measurement (i.e., for example, only with one sensor) is extremely difficult to implement. That is why the following solutions are typically in use: the use of additional monitoring hardware on a current sensor (e.g. by means of comparators), which triggers at a certain amount of excess current or the use of two different current sensors (e.g. a Hall sensor or a shunt-based sensor).
When using additional monitoring hardware, it has been proven disadvantageous that sensors having such an integrated solution are usually expensive proprietary developments which are developed only for electric vehicles and are manufactured in small quantities. In addition, an application comprising such an additional monitoring hardware is generally not flexible enough with regard to the setting of excess current limits. Hence, a time dependent or temperature dependent adaptation is, e.g., not possible.
The use of two different sensor technologies, respectively from two different measurement methods, is the most reliable method to date; however, two different components have to also be installed in this case, which leads to increased costs.
If two identical current sensors are used, faults being caused by a common disturbance could occur when transmitting a detected current, e.g., as a result of external influences (EMV, etc.).
The German patent application DE3422363C2 describes a method for transmitting data in motor vehicles according to the prior art. In said method, data signals are sent as a normal and as an inverted bit sequence. In this case, inverted means that a logical “1” is transmitted as a logical “0” and a logical “0” as a logical “1”. The fault detection results from a comparison of the normal and the inverted bit sequence.
The German patent application DE102011079126A1 describes a battery management system according to the prior art comprising a plurality of measuring units as well as a plurality of second measuring units which are each associated with at least one battery module of a battery in order to acquire a measured variable. The measuring units transmit the measured variables via two separate data lines.
The German patent application DE102011079126A1 describes a battery monitoring device according to the prior art. The transmission of sensor data takes place in said device via a primary serial bus and a redundant secondary serial bus.